Lead alloy



NOV. 10, v\N slNGLETON E1- AL f v LEAD ALLOY Filed July 25,*1955 y l I A @0 zo hg' 1 l ANNEALED somuazoa.

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E 5f 3 a l uw) J 'D W ""'H'S 207 ELoNGATloN PERCENTAGE 417.45% ELoNGATloN PERcENrAGE 0F 6" GAUGE LENGTH OF GAUGE LENGTH [u SCRAP IHM.

o'sszz |l Il" .rl "'I 113/ o-voz 1%' /fvyf/vraks Patented Nov. I0, 1936 LEAD ALLOY William Singleton, Wembley, 9"*12 fw Holme, Buxh Hill Park, and Brinley Eon. Ealing'o London, England, auiznors to Geodlass Wall and Lead Industries Limlted, London, England,

a British company application .my es, was, seem ne. In Great Britain November i9.

26 Chime.

This invention relates to improvements in leadand lead alloys and to processes of manufacturin: and treatingvthe same, and has for its principal object the provision of a lead or alloy o! lead .5 or articles containing the same with improved mechanical properties and greater resistance to corrosive iniiliences. This application is a continuation in part o! our prior application for Letters Ratent Serial No. 641,320, nled November 4th, 1932. It la known that lead can be alloyed with tellurium, but such alloys have not, so far as we are aware, received commercial application prior to the development of the present invention. We have now discovered that lead to which a very small proportion or tellurium has been added'has entirely new properties, even though in auch alloys the proportion of tellurium may be so small y that the material may almost be regarded as lead rather than as an alloy of lead with tellurlum, but i'or convenience in this specification the metal is referred to as a, lead tellurium alloy. It

has also been found that advantages are realized by the addition oi tellurium to conventional alloys of lead Withvother metals, for instance with antimony. tin and cadmium', or alloys of lead with various combinations oi these other metals, such alloys as well as the lead telluriurn alloy being referred to broadly herein as lead-- base alloys.

One very material advantage resulting from the addition of tellurium to lead even when the proportion oi tellurium added is very small, for example of the order of 0.02% oi 'tellurium re sides in the .fact that although the `material as cast is almost as soft as ordinary pure commercial lead it is nevertheless capable ot being per# manently work-hardened or toughened so that it has a much increased tensile strength of over 50% after rolling', the bulk of the increased strength -being permanently retained at ordinary temperatures. The tensile strength of commer cial lead is approximately doubled when tellurium of the order oi 0.06% is added. It is also Il found that lead tellurium alloys within the scope of this invention are in general more resistant' to corrosion by chemically active materials auch as concentrated acids, for instance sulphuric and phosphoric acid, than is ordinary lead. Lead to which n. improved by the adda-m of :einem in accordance with thev present invention ie lese readily attacked by boiling sulphurie acid and even extremely small proportionnel' tellurlnm, such for .example as 0.04% to 0.07% of tellurium.

Il serve toraise the eocalled."ash point of invention lien time.

when subjected to :merio acid, temperatineee of 310 C. or over heinz ary to reach the flash point, while in proportion ofv about 0.07% or over the tellurium imparts to the lead such resistance to attack that it will not iash" even when exposed to'boiline sulphuric acid.

In generalin the practice of our invention we prefer to use quantities of tellnrinm ranging from not substantially below 0.02%. to not cuentan tially above 0.1%. Quantities of teilurium mate riallywln excess of the latter more have been found to develop in lead or lead alloy adveree characteristics unless special precautions are oh served in the preparation of the material. Quantities substantially below that of 0.02% are insumcient for the development of appr improvement from a practical standpoint.

Thus one .of the .principal dimcnltes encourt' tered whenthe percentage of teliurinm is materially greater than 0.1% la the tendency ci? the tellurium izo-segregate when naine the ordinary method of casting. lt is found, for instance, that when the proporti of tellurlnm added to lead or a lead alley dees not exceed 0.l%, the tel lurium is distributed substantially uniformly throughout e, cent billet. On the other hand, lsf the quantity of tellurium he increased to @.l. the billet le found to contain considerably more tellurium in the upper than in the lower por tiene, and this lack of uniform. dintrinution nersiste when the billet ie :subsequently rolled out or extruded into a reiatively thin section. 1i a quantity oi tellurium ae great @50.14% is intro-Y duced,'the irregularity of distribution of the tel-4 'lurium in the cnet billet ie @nite pronounced approaching rather closely that observed when much larger quantities are used. Say up to 0.24%; in other words, there le a rather sharp breek. in the curve representing the tendency of teilw rium to Segmente with o. simili inerente the duantityoi tellnnum over @Jv/0,' and this leek ci? ormity is moet undemrahle. v

It con ne demonetieted then @nenti-.tice

tellan'inm end leed in the neighhenrh 0.@555 to 0.65% represent wenn solubility ci tellnrilnn in leed, het it in tent tc note larger dnantitiee oi millenium un to 0.1% een fee introduced Without indirekte materiel segregation with ordine-ry method o cantine. En inet, ne lieve fennel in @generell that .the optimum quantity ne :ree` garde resistance to coneccion combined with nn@ proved 'rneehenicel chmenteristioe nmol@ and a preferred moge ier the practice of one One of the most important improvements in lead or lead alloys obtained by the addition of tellurium thereto in the indicated proportions is the increased strength, toughness and hardness vlead has a tensile strength of the order of 2,100

lbs. per square inch, and a hardness in the rolled sheet of between four and five on the Brinell scale. An alloy of similar`lead to which 0.02% of tellurium had been added, was found after cold rolling to have a tensile strength of 3,875 lbs. per square inch, and a hardness of seven to eight on the Brinell scale while the addition of 0.04% tellurium to the same lead, gave a product having a tensile strength of 5.000 lbs, per square inch. 'Higher tensile strengths have been observed after cold rolling when larger quantities of tellurium up to 0.1% were added to lead. The increased tensile strength is accompanied by toughness and the worked alloy is ductile up to the limit of 0.1%.

Lead tellurium alloy when extruded or worked at elevated temperatures is soft and varying degrees of toughness may be obtained by varying the temperature of extrusion or` working. It has been observed that when samples of hotextruded lead tellurium alloy Aand commercial lead are tested in a tensile strength testing machine there is marked difference in the behaviour of these two materials. In the case of the former material the uniform distribution of strain as a result of work-hardening is such that the material elongates more regularly and to a considerably greater degree than the commercial lead before fracture takes place. For example when test pieces of the two materials of the same size were tested to breaking point in the same tensile strength testing machine at a rate of elongation of n1 of an inch per minute the lead tellurium alloy showed an increase of in elongation over that of commercial lead, measured over a gauge length of 8 inches. In spite of the reduction of cross section due to this elongation the breaking load, of the tellurium lead test piece, before fracture, exceeded that of the pure lead.

The results of cold work, e. g. higher tensile strength and toughening, would appear in large measure to be retained indefinitely at normal atmospheric temperatures; at elevated temperatures annealing takes place.

If the strength and toughness of the tellurium lead alloy is not fully developed by cold working prior to or in the fashioning of the completed article from which it is formed, the article thus produced is capable of developing additional toughness and strength if subjected to strain or deformation when in use, and this is particularly important where it isgdesired to produce an article having the maximum softness and ductility with latent power to' develop when necessary a materially increased resistance to mechanical strain.

'Ihus"manufactured articles such as pipes or cable sheathing which are formed of alloy, for example, by hot extrusion,=`although soft in their first manufactured state. and easy to work, toughen when subjected to cold work. Consequently, pipes under pressure, if they should yield in any given place, automatically strengthenI themselves at that point, resulting in more even expansion of the pipe. Thus, for example pipes of the alloy have been found to withstand twice the number of freezings before bursting than can be withstood by pipes of ordinary commercial lead treated similarly and at the same time. It is a remarkable property of the alloy that in the soft, i. e. unworked state it has a fatigue resistance nearly three times as great as that of ordinary commercial lead. Long applied stresses -resulting from expansion and contraction, such as are obtained during variation of temperature, cause not only continued deformation of ordinary lead but ultimately fracture. Lead tellurium alloy can withstand such stresses more satisfactorily since the tendency to ilow is automatically checked by the work-toughening of the material. Sheet made from lead tellurium alloy is less liable to thermal creep.

Microscopic examination shows that alloys according to this invention are less susceptible to grain growth, due to heat treatment, than ordinary commercial lead. Due to the fine grain of extruded tellurium lead these products have a very smooth surface and are superior in appear .ance to ordinary commercial lead.

In ordinary lead, when deformed under stress,'

the degree of uniformity of the distribution of deformation depends to a large extent on the uniformity and size of the grains. Uniformity of grain size is not so important wher'e grain siz-e is small since defined grain itself ensures more uniform distribution of deformation, but with large areas of very large grains with adjoining areas of extremely small grains (coarse-grained metal) such as generally occurs in ordinary commercial lead, stresses are not uniformly distributed and therefore the deformation is not uniform.

The addition of tellurium to lead raises the temperature of recrystallization and produces changes in the crystalline structure of the lead which, by making it more difficult for the grains to change their direction of orientation, restrains grain growth. and so reduces considerably the liability to inter-crystalline cracking. The alloy therefore if given initially fine grain retains it and so responds to stress in a more uniform manner than ordinary lead.

The practical effects which result from the foregoing are clearly illustrated in the comparative behaviour of ordinary commercial lead and tellurium lead, when subjected to strain. In the case of ordinary commercial lead, where the structure is generally irregular, strains are unevenly distributed and localized concentration causes recrystalliz-ation so that favourable conditions for intercrystalline cracking are established. In the case of tellurium lead in which there is a refined and uniform structure, strain` is much more evenly distributed so that the concentration of strain., which occurs in ordinary commercial lead, is absent in tellurium lead and the possibility of intercrystalline cracking very markedly reduced.

No difficulty has in the past been experienced in increasing the strength of lead as measured by the effort required to bend or work metal manually, to increase the Brinell hardness, or raise the fatigue limit and alloys of lead with antimony, tin andcadmiu'm and various combinations of the latter have been employed for these purpos for many years. Increased strength in such cases has only been obtained by vsacriiicing softness, ductility, and other inherent and valuable properties which are characteristic of soft lead. It is found, however, that in accordance with the present invention, the characteristics of these alloys of lead with other metals can be substantially improved by the use of small quantities of tellurium of the order hereinbefore mentioned. Thus the present invention contemplates the addition of tellurium to alloys of lead containing antirnony not in excess of 20%, tin not in excess of 70%, or cadmium not in excess of or to ternary alloys such as lead-antimony-cadmium and lead-tin-cadmium, and to quaternary alloys containing all of these elements in which the proportion of any one oi' the elements does not exceed that indicated. The addition oi tellurium is found particularly valuable in lead-base alloys containing a major proportion oi' lead and particularly in those alloys of lead with antimony, cadmium, and/or tin which are commonly employed in pipe or cable sheathing and in which lead is present in amount not less than 85% or 90%.

'Ihe following examples are given as illustrative o1 lead-base alloys Alying within the indicated field which exhibit markedly superior characteristics upon the addition ci' quantities of tellurium not substantially greater than 0.1%.

Eample I Per cent Antimony 1 'Iellurium 0.06 Commercial lead Balance This alloy showed a strength in the cold rolled condition of 5,700 lbs. per square inch with an elongation on an eight inch length of 121/2%. When tellurium was omitted the tensile strength was only 4.550 lbs. per square inch and the elongation Figure 1 shows a stress-strain diagram for the alloy compared with a similar alloy not containing tellurium and this diagram is given as a typical example of the effect of tellurium additions both on plain lead and lead containing other metals such as antimony.

The eliect of annealing for hall' an hour at 200 C. was to cause recrystallization and softening with the result that the alloy containing tellurium had a tensile strength of 3,500 lbs. per

square inch and an elongation of 45%, whereas when tellurium was omitted the tensile strength o1' the sample similarly treated was only 3,080 lbs. per square inch and the elongation 41%. The corresponding stress-strain diagram is shown in Figure 2.

This alloy is suitable for use in extrusion processes owing to the stability imparted by the tellurium to the grain structure at elevated temperatures such as are used in extrusion. The effect of annealing the antimonial lead containing tellurium for half an hour at 200 C. or of (it4 t to produce` a fine grain upon recrystallization,

high temperature treatment such as extrusion is whereas similar annealing when tellurium is absent produces a very coarse grain upon recrystallization, the grain size being quite ten times as great in linear dimensions when.the tellurium is omitted.

Antimony lead alloys are particularly suscera= tible to hot shortness and give serious dilculties during extrusion. The addition of tellurium by producing a fine and stable structure, reduces the liability to hot shortness. and permits aV 4 wider range of extrusion conditions.

" Eample II Per cent Antimony l 8 Tellurium 0.07 Commercial lead Balance This example shows the application of the invention to a high antimony alloy such as is irequently used for its resistance to chromic acid solutions. This alloy, when tested in a chromiumi Example IH The following is an example oi a cadmium lead alloy containing tellurium:-

. Per cent Cadmium 0.5 Tellurium .07 Commercial lead Balance The addition of tellurium to this cadmium alloy had a marked eiIect in increasing the tensile strength and elongation oi' both cold-rolled and annealed materials.

After cold-rolling the strength oi the alloy containing tellurium was 4,000 lbs. per square inch. against 3,500 lbs. per square inch when tellurium was omitted and the elongation was 32.5% against 30%. After annealing for half an hour at 200 C. the tensile strength was 3,820 lbs. per square inch and elongation 45% against a strength of 3,500 lbs. per square inch and elongation of 34%- when tellurium was omitted. Comparison of the gures of the tellurium-lead-cadmium alloy in the rolled and annealed condi- -tion shows that the rolling increased the tenl Example IV The following is an example of a tin alloy.

Per cent Tin 3 Iellurium 0.07 Commercial 'lead Balance This alloy showed marked increase of strength and in. addition showed work hardening properties as compared with an allay from which tellurium was omitted. The tensile strength alter rolling was 5.200 lbs. per square inch and elongation, measured on a length of eight inches, 12%. whereas a 3% tin-lead alloy without tellurium had e. tensile strength of 3,760 lbs. per square inch after rolling with an elongation of 45%.

After annealing tor half an hour at 200 C. the alloy-containing tellurium showed a tensile strength oi 3,930 lbs. per square :inch and an elongation of 429%; While the tin lead alloy tion of 30%.

Resistance to grain growth upon annealing similar to that shown in the previously mentioned alloys was revealed in this case. In other words the alloy is more The alloys of Examples V and VI are solders, Example V being a plumbers solder and Example VI a tinman's solder. They are characterized by a greater fluidity near the solidifylng point than ordinary solder and are therefore easier to work. The tinmans solder runs particularly well under the iron.

Example VII The following is an example of a type or bearing metal.

Percent Tin i Antimony l5 Tellurlum la 0.06 Commercial lead Balance The resistance to recrystallizatlon and to eoarsening of grain under heat which is imparted by telluriuxn is a distinct benefit in metals of this class.

It is found that the addition oi tellurium. in the foregoing alloys not only renders these alloys susceptible to toughening by cold working and therefore produces in them the characteristic properties of the binary lead tellurium alloy, but

the known desirable properties of these alloys are retained. Due to the greater stability of structure imparted to these alloys by the addition of tellurium the invention renders available a more extensive range of extrusion temperatures than hitherto, and in general the alloys are improved in the same ma'nner as is commercial lead when tellurium is introduced.

A further important advantage of the invention lies in the fact that the hardness, strength, or toughness of manufactured lead articles can be controlled. Hard or tough articlesv can be manufactured by cold working the metal, and articles of degrees of toughness or hardness varyg over a wide range can beobtained at will by working at regulated temperatures or variation of extent of working or by cold working with annealing.

The following example is illustrative of the manner in which the characteristics of the material may be controlled:-

Example VIII was rolled from cast ingots six inches thick into stable under heat treat-A the form of sheet about one-eighth of an inch thick and tests were made in comparison with similar lead containing no tellurium. Another ingot ci' the same materials was extruded into strip-form for purposes of comparison. The following table gives the results:-

Elongdation un cr Commer- Commercial lead ggg( cial lead containing straining tllllum (2li per min.)

Tensile Tensile strength strength iba/uq. in. iba/aq. in. Per een: (a 7 days after rolling. 2. 200 4, 000 20 (b As (g) but after annealing 3 ounatl00C 2,300 3,240 37 (c) As (a) but after anneai ys at l 2, 300 3, 136 33 (d) As Se) but after annealing 3 et 150 C 2.800 3,230 35 (c) As (s) but after annealing ay: st 150O 2,300 2,940 34 (f) As (a) but after annealing hours atm 2.300 2,860 35 (a) Al extruded 2, 300 2. 700 55 While as has been hereinbefore indicated, for many purposes the critical upper limit of tellurium is not substantially above 0.1%, as established by the development of certain adverse characteristics of which the most important is the segregation of the tellurium, we may under some circumstances practice our invention by the employment of still greater quantities of tellurium, for instance proportions up to about .25%.A While in the absence of special conditions of preparation these increased quantities of tellurium render the material much less satisfactory, it is nevertheless possible to apply to such alloys the regulatory steps herein suggested whereby substantially the desired degree ci toughness or hardness can be obtained and for some purposes the tendency of the telluriuln to segregate does not constitute a serious disadvantage.

Reference is made herein to special conditions of manufacture which may be observed in the formation of the alloy or the article of which the alloy is composed 'and which have been found to reduce to a material extent the tendency of the tellurium to segregate when employed in quantities materially greater than 0.1%. ne such method of procedure is to cast the molten metal in the form of thin plates, and to immediately chill the cast metal. process substantial uniformity of distribution of the tellurium can be secured and an improvement of the resulting alloy, similar to that described hereinbefore when smaller quantities of telluriurn are used. can be obtained even though quantities of tellurium as high as 2% are added. This procedure is of course applicable not only to the treatment of lead but to the treatment of alloys of lead with tin, cadmium, and antimony as hereinbefore described.

The following example is illustrative of this method as applied to the formation of battery plates, in which held it is particularly suitable owing to the conventional employment of lead in the form of thin plates:-

Example I X It is found that with this Il and was cast with a scrap section I5 along the side which lay uppermost in the mould. An iron mould was used so that the casting was chilled during setting.

The dimensions were as follows:-

Length (horizontally in the drawing) 18 centimetres Width (of active portion of plate) 13 centimetres 4 centimetres Width (of scrap section) Dimensions of terminal lug:

Length 4 centimetres Width 2 centimetres Overall thickness of plate-; 9millimetres On the drawing the percentages o! tellurium which were separately determined in each sectionv It willbe understood that the word lead as` used herein is intended to cover either chemically p ure lead, or electrolytic lead, or lead in the usual commercial form`in which small quantities oi other metals, e. g. copper, nickel and bismuth are sometimes present. It will also be appreciated that in the appended claims it is desired to cover alloys such as those described in which impurities may be present in the completed alloy as Well as in any of the componentsthereof and alloys corresponding to those Ydescribed but containing ingredients which are inert or which do not contribute to the production of a result differing in any material degree from that contemplated by the present applicants.

We claim:-

1. A lead-base alloy consisting substantially of lead and containing a small proportion of tellurium in amount of from about 0.02% to about 0.1% of the whole alloy, said alloy being characterized by increased corrosion resistance and stength and amenability to hardening by cold working as compared with similar lead-base alloys free from tellurium.

2. A lead-base alloy consisting substantially of lead, containing antimony in relatively small and benecial amount, and containing a small proportion oi' tellurium in amount of from about 0.02% to about 0.1% of the whole alloy, said alloy being characterized by increased corrosion resistance and strength and amenability to hardening by cold working as compared with similar lead-base alloys free. from tellurium.

3. A lead-base alloy consisting substantially of lead, containing tin in relatively small and benetlcial amount,`and containing a small proportion of tellurium in amount of from about 0.02% to about 0.1% of the whole alloy, said alloy being characterized by increased corrosion resistance.

and strength and amenability to hardening by cold working as compared with similar lead-baseI alloys free from tellurium.

4. A lead alloy composed entirely of lead and a small proportion of tellurium in amount of from about 0.02% to about 0.1% of the whole alloy, said alloy being characterized by increased corrosion resistance and strength and amenability to hardening by cold working as compared with similar lead-base alloys free from tellurium.

p 5 An extruded elongated tubular article formed of the lead-base alloy described in claim 1.

6. Pipe formed ofthe lead-base alloy described in claim l.

7. Cable sheathing formed of the lead-base alloy described in claim 1.

8. Extruded articles formed of the lead-base alloy described in claim 1.

9. A lead-base alloy consisting substantially of lead, containing antimony in amount not exceeding 20%, and containing a small proportion of tellurium in amount of from about 0.02% to about 0.1% of the Whole alloy, said alloy being characterized by increased corrosion resistance andstrength and amenability to hardening by cold working as compared with similar lead-base alloys free from tellurium.

10. A lead-.base alloy consisting of at least lead, any remainder being composed of at least one metal selected from the group consisting of tin, antimony and cadmium, and a small proportion' of tellurium in amount of from about 0.02% to about 0.1%, said tellurium being distributed substantially uniformly throughout said alloy, said alloy being characterized, as compared with alloys otherwise similar but containing no tellurium, by substantially smaller grain size and by increased resistance to grain growth and intercrystalline cracking.

11. An elongated tubular article formed of a lead-base alloy consisting of at least 85% lead, any remainder being composed of at least one metal selected from the group consisting of tin, antimony and cadmium. and a small proportion of tellurium in amount not exceeding 0.1% and not less than about 0.02%.

12. Pipe formed of a lead-base alloy Aconsisting of at least 85% lead, any remainder being composed of at least one metal selected from the group consisting of tin, antimony and cadmium, and a small proportion of tellurium in amount not exceeding 0.1 and not less than about 0.02%.

13. Cable sheathing formed of a lead-base alloy consistingcf at least 85% lead, any remainder being composed of at least one metal selected from the group consisting of tin, antimony and cadmium, and a small proportion of tellurium in amount not exceeding 0.1%.and not less than about 0.02%.

14. An extruded elongated article formed of a lead-base alloy consisting of at least 85% lead, any remainder being composed of at least one metal selected from the group consisting of tin, antimony and cadmium, and a small proportion oi' tellurium in amount not exceeding 0.1% and not less than about 0.02%.

15. A lead-base alloy consisting substantially of lead and containing a small proportion of tellurium in amount of from about 0.06% to about 0.1% of the whole alloy, said alloy being characterized by increased corrosion resistance and strength and amenability to hardening by cold working as compared with similar lead-base alloys free from tellurium.

16. A lead alloy composed entirely of lead and a small proportion of tellurium in amount of from about 0.06% to about 0.1% of the whole alloy, said alloy being characterized by increased corrosion resistance and strength and amenability to hardening by cold working as compared with similar lead-base alloys free from tellurium.

17. A lead-base alloyA consisting substantially of lead, containing a metal selected from the group consisting of antimony, tin and cadmium, and containing a small proportion of tellurium of the order of from 0.06% to 0.1% of the whole alloy, said alloy being characterized by increased corrosion resistance and strength and amenability to hardening by cold 4working as compared with vrosion resistance and 18. Cold-worked material formed of an alloy consisting substantially oi lead and containing a.

small proportion o! tellurium in amount oi from about 0.02% to about 0.1% of the whole alloy, said alloy being characterized by increased corrosion resistance and strength and amenability to hardening by cold working as compared with similar lead-base alloys free from tellurium.

19. Cold-worked material formed of an alloy consisting substantially of lead and containing a small proportion of tellurium in amount of from about 0.02% to about 0.25% oi' the whole alloy, said alloy being characterized by increased corstrength and amenability to hardening by cold working as compared with similar lead-base alloys free from tellurium.

20. A lead-base alloy composed entirely of lead and a small proportion of tellurium less than 0.25% but not less than about 0.02%, said alloy having increased toughness and strength imparted thereto by cold working.

21.A A lead-base alloy consisting of lead, any remainder being composed of at least one metal selected from the tin, antimony and cadmium, and a small proportion of tellurium in amount less than 0.25% and not less than about 0.02%, said alloy having increased toughness and strength imparted thereto by cold working.

22. A method of permanently increasing to a controlled extent the degree of toughness and strength of a lead-base alloy consisting substan tially of lead and containing a small proportion of tellurium less than 025% but .not less than about 0.02%, which comprises working the alloy to toughen and strengthen the taining a temperature suiiicient to partially oi!- set the toughening and strengthening eiiect oi working.

at least, 85%

group consisting oi same while maincontrolled extent the degree of toughness and strength of a lead-base alloy consisting substantially of lead and containing a small proportion of tellurium less than 0.25% but not less than about 0.02%, which comprises the successive steps of cold working the alloy to toughen and strengthen the same, and heating the alloy suillciently to partially offset the toughening and strengthening eiilect of working.

24. A method of permanently increasing to a controlled extent the degree of toughness and strength of s. lead-base alloy consisting of at least 85% lead, and remainder being composed of at least one metal selected from the group consisting of'tin, antimony and cadmium, and a small proportion of tellurium in amount less than 0.25% andnot less than about 0.02%, which comprises working the alloy same while maintaining a temperature sumclent to partially oiset the toughening and strengthening eiect of working.

25. A method of' permanently increasing to a controlled extent the degree of toughness and strength 0L a lead-base alloy consisting of at least 85% lead, any remainder being composed of at least one metal selected from the group consisting of tin, antimony and cadmium, and a small proportion of tellurium in amount less than 51.25% and not less than about 0.02%, which comprises cold working the alloy to toughen and strengthen 'the same, and thereafter heating the alloy suiciently to partially oii'set the toughening and strengthening eect of working.

26. A lead-base alloy consisting substantially o! lead and containing e. small proportion of telluriuzn in amount of from about 0.02% to about 0.10%, said alloy having increased toughness and strength imparted thereto by cold werking.

WILLIAM SINGLETON. WIILIAM HULME. BREVE? JONES..

toughen and strengthen the 

